Today I went outside in the sweltering heat with my iron and played with Tyvek. I started with a used USPS priority mailer made of Tyvek. I cut small pieces, painted them on one side with Lumiere and let them dry (see the second photo). Then I placed them between layers of my Teflon pressing sheet and ironed them (at medium to high heat), pressing very lightly. I did this OUTSIDE (the fumes are noxious) with a steady breeze for ventilation.
The result is a very lightweight, somewhat flexible, durable piece. They shrink by about 1/3 to 1/2. The bubbles form away from the heat source, so you can choose to have concave bubbles or convex ones on the painted side, depending on which side is down when you iron. If you press hard, you get a flatter, thinner finished piece; mine reminded me of gold leaf. The size of the bubbles seems to depend on how hot the iron is, how long you iron, and how hard you press down. If you iron longer, you get interesting holes.
This afternoon, I sewed a few pieces down to a fabric background, and embellished them with beads and hand-dyed perle cotton to make a little pin (last photo). My friend Grace Howes brought this beautiful fabric and perle cotton back from England for me!